Ink jet printer and ink jet printing method

Abstract

In the ink jet printer, a pressure generation chamber 11 is expanded in a stepped manner, which enables a high speed discharge of a very small ink droplet. Prior to the ink discharge, the pressure generation chamber is contracted so as to enable a high-accuracy gradation printing with a wide range of ink droplet size. A control unit 20 generates: a first contraction signal for contracting the pressure generation chamber 11 without discharging any ink droplet 17; a first expansion signal for expanding the pressure generation chamber 11 to discharge the ink droplet 17; and a second expansion signal to further expand the pressure generation chamber 11 so as to break off an ink column discharged from a nozzle 12 and pull an unnecessary portion of the ink back into the nozzle 12.

What is claimed is:  
     
       1. An ink jet printer comprising: a nozzle for discharging ink; a pressure generation chamber communicating with the nozzle; a common ink tank for supplying ink to the pressure generation chamber; an electro-mechanic converter connected to at least one wall of the pressure generation chamber; and a control unit for applying a drive voltage signal to the electro-mechanic converter; the electro-mechanic converter being deformed by a drive voltage signal from the control unit, so as to expand or contract the pressure generation chamber to discharge ink from the nozzle, and 
       wherein the control unit generates:  
       a first expansion signal which deforms the electro-mechanic converter so as to expand the pressure generation chamber and maintain the expanded state for a predetermined period of time, so that ink is discharged from the nozzle; and  
       a second expansion signal, following the first expansion signal, which deforms the electro-mechanic converter so as to further expand the pressure generation chamber, so that an ink column discharged from the nozzle is broken off at an early stage and an unnecessary portion of the ink is pulled back into the nozzle.  
     
     
       2. An ink jet printer as claimed in claim  1 , wherein the control unit generates a second contraction signal between the first expansion signal and the second expansion signal, so as to deform the electro-mechanic converter to temporarily contract the pressure generation chamber, thus increasing speed of the ink droplet discharge from the nozzle. 
     
     
       3. An ink jet printer as claimed in claim  2 , wherein the control unit generates a third contraction signal following the second expansion signal, so as to deform the electro-mechanic converter to contract the pressure generation chamber, so that residual vibration of the ink meniscus in the nozzle is suppressed. 
     
     
       4. An ink jet printer as claimed in claim  1 , wherein the control unit generates a third contraction signal following the second expansion signal, so as to deform the electro-mechanic converter to contract the pressure generation chamber, so that residual vibration of the ink meniscus in the nozzle is suppressed. 
     
     
       5. An ink jet printer comprising: a nozzle for discharging ink; a pressure generation chamber communicating with the nozzle; a common ink tank for supplying ink to the pressure generation chamber; an electro-mechanic converter connected to at least one wall of the pressure generation chamber; and a control unit for applying a drive voltage signal to the electro-mechanic converter; the electro-mechanic converter being deformed by a drive voltage signal from the control unit, so as to expand or contract the pressure generation chamber to discharge ink from the nozzle, and 
       wherein the control unit generates:  
       a first contraction signal to deform the electro-mechanic converter so as to contract the pressure generation chamber without discharging ink from the nozzle; and  
       a first expansion signal to deform the electro-mechanic converter so as to expand the pressure generation chamber and maintain the expanded state for a predetermined period of time, so that ink is discharged from the nozzle.  
     
     
       6. An ink jet printer comprising: a nozzle for discharging ink; a pressure generation chamber communicating with the nozzle; a common ink tank for supplying ink to the pressure generation chamber; an electro-mechanic converter connected to at least one wall of the pressure generation chamber; and a control unit for applying a drive voltage signal to the electro-mechanic converter; the electro-mechanic converter being deformed by a drive voltage signal from the control unit, so as to expand or contract the pressure generation chamber to discharge ink from the nozzle, and 
       wherein the control unit generates:  
       a first contraction signal to deform the electro-mechanic converter so as to contract the pressure generation chamber without discharging ink from the nozzle;  
       a first expansion signal to deform the electro-mechanic converter so as to expand the pressure generation chamber and maintain the expanded state for a predetermined period of time, so that ink is discharged from the nozzle; and  
       a second expansion signal, following the first expansion signal, so as to deform the electro-mechanic converter to further expand the pressure generation chamber, so that an ink column discharged from the nozzle is broken off at an early stage and an unnecessary portion of the ink is pulled back into the nozzle.  
     
     
       7. An ink jet printer as claimed in claim  6 , wherein the control unit generates a second contraction signal between the first expansion signal and the second expansion signal, so as to deform the electro-mechanic converter to temporarily contract the pressure generation chamber, thus increasing speed of the ink droplet discharge from the nozzle. 
     
     
       8. An ink jet printer as claimed in claim  6 , wherein the control unit generates a third contraction signal following the second expansion signal, so as to deform the electro-mechanic converter to contract the pressure generation chamber, so that residual vibration of the ink meniscus in the nozzle is suppressed. 
     
     
       9. An ink jet printing method using an ink jet printer comprising a nozzle for discharging ink; a pressure generation chamber communicating with the nozzle; a common ink tank for supplying ink to the pressure generation chamber; an electro-mechanic converter connected to at least one wall of the pressure generation chamber; and a control unit for applying a drive voltage signal to the electro-mechanic converter; the electro-mechanic converter being deformed by a drive voltage signal from the control unit, so as to expand or contract the pressure generation chamber, so that ink is discharged from the nozzle, 
       the method comprising:  
       a first expansion step in which the electro-mechanic converter is deformed by a signal from the control unit to expand the pressure generation chamber and maintain the expanded state for a predetermined period of time, so that ink is discharged from the nozzle, and  
       a second expansion step following the first expansion step, wherein the electro-mechanic converter is deformed by a signal from the control unit to further expand the pressure generation chamber, so as to break off an ink column to be discharged from the nozzle at an early stage and pull an unnecessary portion of ink back into the nozzle.  
     
     
       10. An ink jet printing method as claimed in claim  9 , the method further comprising a second contraction step between the first expansion step and the second expansion step, wherein the electro-mechanic converter is deformed to temporarily contract the pressure generation chamber so as to increase speed of an ink droplet to be discharged from the nozzle. 
     
     
       11. An ink jet printing method as claimed in claim  10 , the method further comprising a third contraction step following the second expansion step, wherein the electro-mechanic converter is deformed by a signal from the control unit to contract the pressure generation chamber so as to suppress residual vibration of the ink meniscus in the nozzle. 
     
     
       12. An ink jet printing method as claimed in claim  9 , the method further comprising a third contraction step following the second expansion step, wherein the electro-mechanic converter is deformed by a signal from the control unit to contract the pressure generation chamber so as to suppress residual vibration of the ink meniscus in the nozzle. 
     
     
       13. An ink jet printing method using an ink jet printer comprising a nozzle for discharging ink; a pressure generation chamber communicating with the nozzle; a common ink tank for supplying ink to the pressure generation chamber; an electro-mechanic converter connected to at least one wall of the pressure generation chamber; and a control unit for applying a drive voltage signal to the electro-mechanic converter; the electro-mechanic converter being deformed by a drive voltage signal from the control unit, so as to expand or contract the pressure generation chamber, so that ink is discharged from the nozzle, 
       the method comprising:  
       a first contraction step in which the electro-mechanic converter is deformed by a signal from the control unit to contract the pressure generation chamber without discharging any ink from the nozzle, and  
       a first expansion step following the first contraction step, wherein the electro-mechanic converter is deformed by a signal from the control unit to expand the pressure generation chamber and maintain the expanded state for a predetermined period of time, so as to discharge ink from the nozzle.  
     
     
       14. An ink jet printing method using an ink jet printer comprising a nozzle for discharging ink; a pressure generation chamber communicating with the nozzle; a common ink tank for supplying ink to the pressure generation chamber; an electro-mechanic converter connected to at least one wall of the pressure generation chamber; and a control unit for applying a drive voltage signal to the electro-mechanic converter; the electro-mechanic converter being deformed by a drive voltage signal from the control unit, so as to expand or contract the pressure generation chamber, so that ink is discharged from the nozzle, 
       the method comprising:  
       a first contraction step in which the electro-mechanic converter is deformed by a signal from the control unit to contract the pressure generation chamber without discharging any ink from the nozzle,  
       a first expansion step following the first contraction step, wherein the electro-mechanic converter is deformed by a signal from the control unit to expand the pressure generation chamber and maintain the expanded state for a predetermined period of time, so as to discharge ink from the nozzle, and  
       a second expansion step following the first expansion step, wherein the electro-mechanic converter is deformed by a signal from the control unit to further expand the pressure generation chamber, so as to break off the ink column to be discharged from the nozzle at an early stage and pull an unnecessary portion of the ink back into the nozzle.  
     
     
       15. An ink jet printing method as claimed in claim  14 , the method further comprising a second contraction step between the first expansion step and the second expansion step, wherein the electro-mechanic converter is deformed by a signal from the control unit to temporarily contract the pressure generation chamber so as to increase speed of an ink droplet to be discharged from the nozzle. 
     
     
       16. An ink jet printing method as claimed in claim  14 , the method further comprising a third contraction step following the second expansion step, wherein the electro-mechanic converter is deformed by a signal from the control unit to contract the pressure generation chamber so as to suppress residual vibration of the ink meniscus in the nozzle.